The cold stare of Dr. Doris Haggis-on-Whey dominates the cover of Cold Fusion, Volume 4 in The Haggis-On-Whey World of Unbelievable Brilliance series from McSweeney’s Books. Dr. Doris’s schlemiel-nonpareil husband, Benny, gazes from the cover too, with the threat of a drool.

Dr. Doris states the premise of the new McSweeney’s book:

“Cold fusion is so crucial to our very existence that only a few people know or care about it. Cold fusion affects reptiles, agriculture, the molecules we use to butter our toast, and television.”

The Eggers boys are at it again—Dave and Toph, launching their latest assault on scientific reason and the American giggle box. Cold Fusion thus joins other distinguished Haggis-On-Whey titles such as: Giraffes? Giraffes!; Your Disgusting Head: The Darkest, Most Offensive—and Moist—Secrets of Your Mouth, Nose and Ears; and Animals of the Ocean, in Particular the Giant Squid.

It’s tempting to imagine Dave, 39, and Toph, 26, creating these like kids in a traditional, all-American childhood. You know, nights at camp, Dave in an eagle-scout uniform, Toph in the top bunk, both boys laughing all night, fit to bust, blurting out sleepy, goofy thoughts:

Dave: Okay, so what things are made immediately better with cold fusion?

Toph: Reggae music. Interracial dating. Fruit bats

But they never had that all-American childhood. Instead, they lost both to cancer in a 32-day period, leaving Dave—in his early 20s, with deep misgivings and more than a few sobering mistakes—to don a superhero costume (De Facto Dad!) and steward his eight-year-old bro.

Turns out the brothers raised one another, and their experience is recounted in A Heartbreaking Work of Staggering Genius, the 2001 pseudo-memoir that made Dave Eggers famous and, yes, the de facto voice of a generation of young writers.

Dave and Toph—along with Dave’s wife, Vendela Vida, a respected novelist and co-editor of The Believer—now comprise the First Family of American Hip Lit. Dave has now written four books and one short-story collection and edits McSweeney’s, the hugely influential quarterly magazine and book-publishing company. He’s also co-founder of 826 Valencia, a network of nonprofit writing and tutoring centers for young people.

Toph?

“I graduated UC Berkeley in 2006,” he says, “and went to work for Judd Apatow and Spike Jonze, then struck out on my own to make short.” (He’s currently developing a feature film of the Haggis-on-Whey series for the Montecito Picture Company.)

“In every book, we include a next-book series where we make up 60 book titles,” Dave says. “Concrete Mixing. Zinc Extraction. Horse Stable Architecture. The most banal ideas. After we settle on one, like cold fusion, we have a torture technique we use on each other. We send a title, something like ‘What’s the best place for birds to do cold fusion?’ Then we force the other person to write about the title.”

That’s how the sausage gets made. But who buys it? Rabid, feral kids, of course. Boys and girls, age 10 and 11, love the books. And their passion poses a conundrum.

“We make a series of fake reference books for kids, books with no real educational value,” Dave says, “but it’s kids who love them and read them most.”

But wait, there’s something really important to know here. Which brother is funnier?

“I think we both know that Toph is funnier,” Dave says.

Toph does not comment.

“Humor relies on a large amount of surprise,” Dave goes on. “If you expect it, it’s not as funny.”

Toph says nothing.

“Toph is the best at coming up with what just makes no sense whatever. From one sentence to the next, you don’t know what you’re going to get.”

Mannequin fights! You can almost hear Toph thinking. A typical Doris Day! A dog and a weasel eating ham